Photovoltaic cells, commonly known as solar cells, are well known devices for direct conversion of solar radiation into electrical energy. Generally, solar cells are fabricated on a semiconductor wafer or substrate using semiconductor processing techniques to form a p-n junction near a surface of the substrate. Solar radiation impinging on the surface of, and entering into, the substrate creates electron and hole pairs in the bulk of the substrate. The electron and hole pairs migrate to p-doped and n-doped regions in the substrate, thereby generating a voltage differential between the doped regions. The doped regions are connected to conductive regions on the solar cell to direct an electrical current from the cell to an external circuit coupled thereto.
Efficiency is an important characteristic of a solar cell as it is directly related to the capability of the solar cell to generate power. Likewise, efficiency in producing solar cells is directly related to the cost effectiveness of such solar cells. Accordingly, techniques for increasing the efficiency of solar cells, or techniques for increasing the efficiency in the manufacture of solar cells, are generally desirable.
The efficiency of solar cells may be improved by using high-quality crystalline silicon substrates to fabricate the solar cells. For example, solar cells fabricated using single-crystalline silicon wafers are generally more efficient than solar cells fabricated using multi-crystalline silicon wafers. The Czochralski technique has been widely adopted by the photovoltaic industry to make single-crystalline substrate, mainly because it is currently more cost effective than the less widely adopted float zone technique. However, the float zone technique can result in single-crystalline substrates of higher quality than those produced by the Czochralski technique, and thus, could become a preferred process for growing single-crystalline silicon materials if the cost efficacy of the process is improved.